1. Field
The disclosure relates generally to the field of coordinated beamforming in multiple-antenna and multiple-cell networks, and, in particular, relates to systems and methods of iterative coordinated beamforming with limited cooperation in multiple-antenna and multiple-cell networks.
2. Background
Wireless cellular systems, e.g., 3GPP LTE-Advanced, implementing multiple antennas and multiple cells may use coordinated processing to provide high data rates and robustness to a user or mobile station (MS) located at the cell edge. In coordinated multicell processing, base stations cooperate to mitigate interference from adjacent cells and fading. If each base station (BS) and each MS is equipped with multiple antennas, beamforming/precoding can be used as a form of multicell cooperation, offering improved throughput compared to the traditional approaches of cellular network planning, such as frequency reuse, sectoring, or spread spectrum. The design of jointly optimized transmit and receive beamforming/precoding schemes, though, is a challenging task.
In coordinated beamforming (CBF), each MS receives a single stream of data from the serving BS, and cooperating BSs can coordinate to mitigate the other-cell interference. Multiple antennas at the MS further helps mitigating inter-cell interference, even with the use of a linear receive filter. Such a system model becomes more and more practical as the MS may see more cell edges due to the deployment of smaller cells in the next generation wireless cellular systems. Mitigating more diverse and stronger out-of-cell interference is the key to improve the performance of MSs located in the cell edge region.
For a K-user (K>1) interference channel with multiple antennas, network utility, such as (weighted) sum rate, is one of the most commonly considered performance measures. Under this objective, many algorithms are proposed for the purpose of the sum mean square error (MSE) minimization, minimum MSE (MMSE) interference alignment, max-min weighted SINR, (signal-to-interference-and-noise ratio) interference-aware coordinated beamforming, and iterative precoder optimization. Joint transmit/receive beamforming vector design to maximize the sum rate in K-user multiple-antenna multiple-cell networks is still an open problem requiring a lot more studies and innovations. In particular, the cost of cooperation is often neglected in most of the previously proposed algorithms.